Not Applicable
Not Applicable
1. Field of the Invention
This invention is related to a generating system for a fuel cell, in particular to a heat waste recirculating system within a generating system used in a proton exchange member fuel cell. The recirculating system effectively utilizes heat waste generated from a conventional fuel cell for reducing electrical energy that may be required by the fuel cell, and enhancing the generating efficiency of the entire system.
2. Description of the Related Art
With the rapid growth of human civilization the consumption of traditional energy sources, such as coal, oil and natural gas, increases rapidly. This results in serious pollution to the global environment and causes various environmental problems such as global warming and acid rain. It is now recognized that the existing natural energy resources are limited. Therefore, if the present rate of energy consumption continues, all existing natural energy sources will be exhausted in the near future. Accordingly, many developed countries are dedicated to the research and development of new and alternative energy sources. The fuel cell is one of the most important and reasonably priced energy sources. Compared with traditional internal combustion engines, the fuel cell has many advantages such as high-energy conversion efficiency, clean exhaust, low noise, and no consumption of traditional gasoline.
In brief, a fuel cell is an electrical power generation device powered by the electrochemical reaction of hydrogen and oxygen. Basically, the reaction is an electrochemical reaction of the electrolysis of water, to convert the chemical energy into electrical energy. The basic structure of a fuel cell, for example, a proton exchange membrane fuel cell, comprises a plurality of cell units. Each cell unit comprises a proton exchange membrane (PEM) at the middle, with the two sides thereof provided with a layer of catalyst, each of the two outsides of the catalyst is further provided with a gas diffusion layer (GDL). An anode plate and a cathode plate are further provided at the outermost sides adjacent to the GDL. After combining all the above elements together, a cell unit is formed. For the practical application of a fuel cell, a plurality of the above cell units are stacked and serially connected to provide sufficient power, as illustrated. Therefore, two adjacent cell units can share a common polar plate, which serves as the anode and the cathode for the two adjacent cell units respectively. Accordingly, such a polar plate is usually referred to as a bipolar plate. Generally, the two sides of the bipolar plate are provided with many grooves for transporting the gases for reaction, such as hydrogen and air (to provide oxygen), as well as transporting the reactants, such as water droplets or vapor, out of the bipolar plate.
One gas supply system for use in a fuel cell comprises: a cathode gas supply system (such as an oxygen supply), and an anode circulation system (such as a hydrogen circulation system), as illustrated in FIG. 1. Atmospheric air may serve as a supply of the oxygen supply system 30, where air is filtered by a filter 32 and than pumped into the fuel cell 50 through a blower 34. Excessive air, upon reaction within the fuel cell 50, is discharged into a water recuperator 36. The water recuperator 36 may recuperate the minute amount of water contained within the discharged air, where the water is then discharged with the hot water, a reactant of the fuel cell 50. Part of the hot water flows through a radiator and then re-enters the fuel cell 50 to construct a cooling system to reduce the heat generated by the fuel cell 50.
The anode circulation system includes: a hydrogen source 40 which regulates hydrogen input through a pressure regulator 42; a hydrogen pump 44 being provided at another end of the fuel cell 50 for discharging excessive hydrogen, upon reaction within the fuel cell, and for pumping the hydrogen source 40 into the fuel cell 50. The excessive hydrogen is discharged through a humidifier 46, then flows back into the piping of the hydrogen supply to be mixed with fresh hydrogen, and then repeats the same circulation.
One known device for storing the anode gas (hydrogen) is to adopt a hydrogen container filled with pressurized hydrogen. An external valve and a hydrogen pump 44 then cooperate to discharge hydrogen that is supplied to the anode gas circulation system. However, such a design for releasing hydrogen, usually, cannot ensure that the hydrogen will be supplied at a constant pressure and in a constant flow rate thereby resulting in waste and reducing generation efficiency.
A steady hydrogen supply system capable of supplying hydrogen at a constant pressure and constant amount, without requiring additional components, is thus needed.
The major technical content of this invention is to use the so-called metal hydride that is filled in the anode gas supply. Metal hydride is able to discharge hydrogen at a pressure corresponding to the temperature that it experiences; the process of releasing hydrogen is an endothermic reaction. When the hydrogen stored within the metal hydride has been completely exhausted, pure hydrogen can be re-charged back to the metal hydride; the process of charging hydrogen is an exothermic reaction. The temperature of metal hydride experiences is positively proportional to the pressure of the hydrogen. Such a proportional relationship may vary among metal hydride furnished by different suppliers. Therefore, while using an anode gas supply of this type, heat energy must be furnished to the anode gas supply in order to discharge the anode gas required by the electrochemical reaction.
In other words, this invention uses the heat waste generated by the fuel cell, as the heat source required by the metal hydride. That is, hot water, a bi-product of the electrochemical reaction of the fuel cell, is used to discharge the anode gas of the anode gas supply. After the hot water is cooled, the coolant is then transported back to the fuel cell to reduce the temperature of the fuel cell, thereby forming a waste-heat recirculation. Such a configuration does not change the basic construction of the original cooling system, but does provide a steady heat source required by the anode gas supply.
It is, thus, a primary objective of this invention to use the thermal, a bi-product of the electrochemical reaction of the fuel cell, as the heat energy for releasing the anode gas of the anode gas supply, thereby constructing a self-sufficient heat energy supply system, reducing manufacturing cost, eliminating the use of electrical power consumed by the fuel cell, and enhancing the efficiency of the entire system.
It is a further objective of this invention to join the self-sufficient heat energy supply system to the cooling system of the fuel cell, so as to effectively implement metal hydride technology in constructing a heat waste recirculation and cooling system that does not lose any heat energy and that does not require additional equipment.
The structures and characteristics of this invention can be realized by referring to the appended drawings and explanations of the preferred embodiments.